The invention relates to an apparatus for determining the crystalline and polycrystalline materials of an item.
To assure safety in air travel, for example, it is necessary to check luggage (object) with travel items (items), particularly for explosive agents or materials, by employing the most modern technical equipment.
A useful technique for checking for explosives is X-ray diffraction, in which X-rays that are scattered at the crystal structure of an item are measured and compared to the characteristic energy spectra of known explosives. Thus, the spectra of the diffracted rays can indicate the presence of an explosive, and provide information about the explosive material in the object.
An apparatus for executing this method is known from DE 195 10 168 A1. Here, at least one collimator generates a fanned X-ray beam from an X-ray source, which then irradiates a test region of a material to be tested. On the side of the test region opposite the X-ray source, slot-shaped collimators are disposed symmetrically around the axis of the central X-ray beam, in a plane extending perpendicular to the fan plane of the X-ray beam. A plurality of detectors performs an evaluation over the entire X-rayed test region.
EP 0 354 045 A2 also discloses an apparatus and a method in which a fanned X-ray beam is generated. As this fanned X-ray beam radiates through the object to be tested, it is diffracted at the lattice structure of the object. A plurality of detectors records the diffraction as an energy spectrum.
A further apparatus is disclosed in U.S. Pat. No. 4,956,856. In this case, a narrow X-ray beam (pencil beam) is generated, and directed, by a rotating roller having a spiral-shaped slot, at an object to be X-rayed. The pencil beam passes through the slot transversely to the object to be tested.
DE 41 01 544 A1 discloses the use of a primary beam having a small cross section in an X-ray device. Here, a plurality of detectors and a concentric collimator arrangement detect the scatter radiation generated from the primary beam.
A drawback of the aforementioned apparatuses for checking luggage is that the entire piece of luggage must always be sampled or scanned by X-ray diffraction in order to ascertain all unacceptable luggage items.
An arrangement for generating an expanded X-ray bundle is known from DE 41 30 039 A1. A collimator arrangement used for this purpose comprises two limiting bodies, which are oriented relative to one another such that they limit a space corresponding to the shape of the ray bundle. This arrangement serves to increase the surface impacted by the X-ray.
It is an object of the invention to provide an apparatus of the general type discussed above, for quickly determining the crystalline and polycrystalline materials of an item.
The above object generally is achieved according to the present invention by an apparatus that includes a diffraction apparatus with a collimator/detector arrangement, an X-ray source that is aimed at the collimation/detector arrangement, and a computer. The collimation/detector arrangement is adjustable, both laterally and height-wise relative to the X-ray source, by first adjustment elements. Additionally, the X-ray source is laterally adjustable, by second adjustment elements. Finally, the first and second adjustment elements are synchronously adjustable and are computer controlled by the computer.
The concept underlying the invention is a diffraction apparatus, comprising a collimator/detector arrangement and an X-ray source that is aimed at this arrangement, and which can be brought into and aligned within a testing stage of an X-ray machine through adjustments in height and transverse position. X-ray diffraction is used to determine the material of an item at a predetermined location. To this end, the lateral positions of collimator/detector arrangement and the X-ray source can be adjusted synchronously, with the collimator/detector arrangement also preferably being adjustable in height relative to the X-ray source.
If only two coordinates of a predetermined location (e.g., belt position X and beam to define the lateral position) are known, the adjustable diffraction unit continuously scans the missing third coordinate by moving the collimator/detector arrangement along the measuring path determined by the two coordinates. Consequently, the materials positioned on this line or path can be measured and determined location dependently. If three coordinates of the predetermined location are known, the diffraction apparatus is aimed at this point, and the type of material of the item is determined by, for example, X-ray diffraction analysis, without the need of a measuring sweep.
The height-adjustable collimator/detector arrangement preferably comprises an adjustable round-slot collimator in the form of a truncated cone with a detector disposed behind it.
In a further step of the analysis of the material of an item using the collimator/detector arrangement, additional information on the material can be obtained if, in addition to the diffraction spectrum, the average atomic number of the material is known. For this purpose, the round-slot collimator has a central opening, which is closed to the detector and in which two different, separate detector devices are disposed one behind the other. In a known manner, these detector devices determine the average atomic number of the object located in the primary beam.
The invention is described in detail below with reference to an embodiment illustrated in the drawing.